Warm Up 9/20

•Draw the Bohr Model for Aluminum

•What is the difference between a hypothesis and a theory?

The Quantum Mechanical Model Chemistry

Bohr’s Model

•Bohr energized hydrogen electrons

(1 e- per atom)

•Energized electrons jumped certain distances from the nucleus

Bohr’s Model

•Bohr saw 4 colors

•Each color has a specific wavelength

Bohr’s Model

•Each wavelength corresponds to a distance from the nucleus

•These distances are called “shells” or “energy levels”

Bohr was wrong

•While Bohr’s theory worked for hydrogen, it could not be applied to any other element because they all have more than one electron

Werner Heisenberg• 1927, Germany• Heisenberg

Uncertainty Principle = It is impossible to determine simultaneously both position and velocity off an electron or any other particle

Heisenberg’s Uncertainty Principle• It’s impossible to

determine where any one electron is at any point in time.

•Scientists talk about probabilities of electrons locations (electronic cloud).

Erwin Schrödinger

•Physicist from Austria

•Late 1920’s•Wrote an equation

to describe the probable location of an electron

Quantum Mechanical Model

•Current Electron Theory

•Created by Schrödinger

•Involves Quantum Numbers

•Can be shown using Electron Configurations (ex: 1s22s22p5)

Quantum Numbers• Each electron is

located in an energy level (n), which is within a sub-level with a shape (l).

Quantum Numbers• A sub-level is made of

orbitals. Different electrons within the same sub-level will have a different orientation (ml) depending on the orbitals orientation within the sub-level.

• Each orbital can have 2 electrons max, but they have opposite spin (ms)

Quantum Mechanical Model • Electrons are

arranged into Energy Levels or Shells (1, 2, 3, 4, …).

• The “Principal Quantum Number” (symbolized by n) indicates the main energy level occupied by the electron

Quantum Mechanical Model• Energy Levels contain

sub-levels (s, p, d, f)

• The “Azimuthal or Angular Momentum Quantum Number” (symbolized by l) indicates the shape of the sub-level

NRG Sub-level “s”Azimuthal Quantum Number 0

“s” sub-level

• l = 0•Sphere shape•Contains 2 e-•One Orbital

NRG Sub-level “p”Azimuthal Quantum Number 1

“p” sub-levell = 1

Contains maximum 6 e-3 orbitals

NRG Sub-level “d”Azimuthal Quantum Number 2

“d” sub-levell = 2

Maximum 10 e-5 orbitals

NRG Sub-level “f”Azimuthal Quantum Number 3

“f” sub-levell= 3

Maximum 14 e-7 orbitals

Quantum Numbers• Magnetic Quantum

Number (ml) indicates the orientation of an orbital around the nucleus

• For example, the sub-level “p” is composed of 3 different orbitals (px, py, and pz)

• Scientists use the values -1, 0, and +1 to tell the orbitals apart.

Practice with Magnetic Quantum Numbers• What would be the

magnetic quantum number used for the s sub-level?

• What would be the magnetic quantum numbers used for the d sub-level?

Spin Quantum Number, ms

• A maximum of 2 electrons can fit into each orbital. BUT electrons don’t like each other (repel)

• 2 spins = +1/2 (up) and -1/2 (down)